Pathology notes

BONE MARROWKinyanjui kamau..HEMATOPOIETIC SITESEmbronic periodFrom 2nd wkYolk sac3rd month to first2wks after birthLiver and spleen4th & 5th monthcommencement in the BM,becomes fully activeby 7th & 8th monthsChildhood & adultlifeBM.The spleen and liver can also resume their foetalhaematopoietic role in certain pathologic conditionsand is called extramedullary haematopoiesis.In the bone marrow, developing blood cells aresituated outside the marrow sinuses, from whereafter maturation they enter the marrow sinuses,the marrow microcirculation and thence releasedinto circulation.HEMATOPOIETIC STEM CELLSHaematopoieisis involves two stages:mitotic division or proliferation, anddifferentiation or maturationstem cells express a variety of cell surfaceproteins such as CD34 and adhesion proteinswhich help the stem cells to home to the BMwhen infused.The stem cells have the appearance of smallor intermediate-sized lymphocytes and theirpresence in the marrow can be demonstratedby cell culture techniques by the growth ofCFU pertaining to different cell lines The bone marrow provides a suitableenvironment for growth and development ofstem cellsThe stem cells have the capability ofmaintaining their progeny by self-replication.Myeloid haematopoiesis is regulated byendogenous glycoproteins called as growthfactors, cytokines and hormonesErythropoietin Granulocyte colony-stimulating factor (G-C